The present invention relates to an automated system to sense the operating conditions within a combustion system of a gas turbine and adjust or tune the combustion system to achieve desired operation or performance.
Industrial combustion or gas turbines are commonly used in many applications, for example, to drive electrical generators in power plants. Many of these gas turbines achieve low emission levels, such as the emission of NOx, by employing lean premixed combustion wherein fuel and an excess of air are mixed prior to combustion to control and limit thermal NOx production. This class of combustion systems or combustors—often referred to as Dry Low NOx combustors, requires careful management of combustion conditions to achieve stable operation and acceptable NOx and CO emissions, while also remaining free of pressure oscillations—called “combustor dynamics” or, simply, “dynamics”—which usually include a combination of acoustics and unsteady energy release during the combustion process. Such systems often require multiple independently controlled fuel injection points supplied by multiple fuel circuits or fuel nozzles in each of one or more parallel combustors in order to achieve desirable combustion performance over the range of operating modes, for example, between start-up and full load. Although these combustion systems have shown to be a great benefit from a standpoint of emissions, the operational envelope of the systems is substantially reduced when compared to more conventional combustion systems. Consequently, the control of fuel conditions and delivery, such as how the fuel is distributed and injected into the combustion zones by the various nozzles—also known as “fuel splits”—have become critical operating parameters and, generally, require frequent adjustment, when, for example, ambient atmospheric conditions, such as temperature, humidity and pressure, change, the gas turbine degrades with usage, fuel composition changes, or other variables are introduced. The adjustment of the combustion fuel conditions, distribution and injection to account for these changes is termed “combustion tuning” or, simply, “tuning”.
Controlled operation of a combustion system generally employs a manual setting of the operational parameters related to a gas turbine's combustion system at several expected or standard operational conditions. Such adjustment or tuning of the combustion system generally requires technicians and specialized instrumentation and takes a day or longer to accomplish. Nevertheless, while the arrived at settings may prove satisfactory at the time of setup, changing conditions—such as, for example, changes in ambient conditions, changes in the condition of the equipment, and unexpected operating conditions—may produce unacceptable performance in a matter of days or weeks, which may necessitate another costly manual tuning. Some of these conventional approaches may employ algorithms and/or physics-based models to predict emissions and other outputs based on current gas turbine operating parameters and, from this, select or modify set points, for example, related to fuel distribution or overall fuel/air ratio. These approaches, however, fail to take advantage of real-time data related to combustor dynamics and emissions, which results in the predictions producing control solutions that lead to increased dynamics and unanticipated emissions excursions within the combustion system. The pressure pulsations related to such dynamics can have sufficient force to harm or degrade the combustion system and dramatically reduce the life of combustion hardware, while such emission excursions can lead to costly permit violations.
Therefore, systems and methods that promote combustion stability, decreased dynamics, and/or improved emission levels remains a technical area of need and high interest within the industry. Moreover, systems and methods that operate by utilizing near real-time data, taken from the turbine sensors, to adjust fuel splits, fuel temperature, overall fuel/air ratio, and/or other variables in order to optimize combustion system performance would have significant value.